Came across this thread while searching for something else. I just ran into this same issue a week or so ago when upgrading a site. I uploaded a patch a few days ago which changes the parameter types for acs_message__edit and solved the problem for me. I also fixed a version problem with the last acs-messaging upgrade script. The patch is at:
https://openacs.org/bugtracker/openacs/patch?patch_number=204
I know Dave's removing GC's acs-messaging dependencies soon but it'd be great if someone could take a look at this for 4.6.4.
